Pathloss 4.0 Frequently ask

11. ) SUBJECT : 10 m DEM


Question :

Where do I find 30 and 10 meter USGS DEM sources that are compatible with Pathloss? (1:24000 scale 7.5 minute sources).



I have looked at the USGS web site and everything is using SDTS DEM which are tar'd and gnuzip'd (xxxxxxx.DEM.SDTS.TAR.GZ). These files, when extracted become .ddf files and these are not compatible with PathLoss. The USGS explains that the previous DEM files had coordinate adjustment errors so I don't want to look at old DEM files.

Answer :

Try www.micropath.com

If you haven't found this already, you need to get this nifty little utility.


SDTS2DEM.exe

First you use WinZip to extract all the .ddf files from the xxxxx.tar.gz file,

then you run the SDTS2DEM.exe program (under DOS) to convert it to a xxxx.dem

file. Then, you can go in to the PathLoss Database menu system and do an

ASCII to Binary conversion on the DEM file that you just created. It will convert it

into a file format that it can use - probably a .dta file.



Works on the 10meter files, but I've had no luck with the 30meter files. But, I'm

using Ver 3.0 of PathLoss, not 4.0.



I get all my SDTS files from GISDataDepot



http://www.gisdatadepot.com/catalog/US/sublist.html



12. ) SUBJECT : HYBRID DIVERSITY

Question:

In Pathloss 4, antenna configuration:TR-TRTH or TRTH-TR is defined as for a hybrid diversity configuration which uses frequency diversity in both directions and space diversity at one end of the path only.



In ITU P.530-8 the FD+SD diversity is specified for 2 receivers and 4 receivers separately in calculating outage probability. I used the above antenna configuration for 2 receivers, but I couldn't find any calculation for 4 receivers in Pathloss.



I'll appreciate if anybody can help me with this. Thanks.



Answer :

The configuration you describe is Quad Diversity. Antenna configurations should be TXRX-TXRX and configured with nominal SD. In the Worksheets module select Operations Diversity Calculation and specify the frequency diversity difference.



The resulted Worksheet Report will provide the effective receive level and reliability for Quad Diversity for each receiver.

Tank you very much for the reply. As a matter of fact, I had tried to use TRDR-TRDR configuration and specify the FD spacing for calculation before I posted the question in the Forum.



Unfortunately, the calculation result was not much different from that of 2-receiver. Moreover, it did not match the hand calculation that I did on the Excel worksheet according to ITU P.530-8 recommendation, either. Any idea?

If you check the help under antenna configurations it will show TXRX-TXRX as two antennas at each site both transmitting and receiving. Most Quad configurations that I have come across transmit one frequency on each antenna with two receivers, one on each receive frequency.

TRDR-TRDR is normally used for space diversity, Where the second antenna is receive only.

Hope this helps. Try it again with TX-RX and see if the results are more in line with your spread sheet.